refactor: own Worker and Ticket service contracts outside providers

Move shared control/lifecycle/observation/Ticket contracts into feature::contracts. Consumers and host bindings import the neutral owner; providers retain current authorization, explicit combined routing and persisted composition.

Document stable semantic IDs and exact compatibility epochs; connect consumer requirements to the existing planner without a new resolver. Exercise consumer installation/dispatch with contract-only test providers, atomic rejection paths, and parsed-source architecture guards including negative fixtures.

Validation: worker and worker-runtime normal tests and doctests passed; root cargo check, rustdoc with warnings denied, fmt, diff and state-contract names passed. Dependent Server authorization tests require separate stale native-v1 fixture updates captured next.

crates/worker-runtime/src/worker_backend.rs

@@ -144,9 +144,11 @@ use workdir::{
 use worker::WorkerController;
 use worker::feature::builtin::manage_workdir::WorkspaceAttachedWorkdirSession;
 use worker::feature::builtin::{
-    CompositeWorkerObservationProvider, WorkerObservationError, WorkerObservationProvider,
-    WorkerObservationSubject, WorkerObservationSubjectRef, WorkerSessionCapture,
-    WorkspaceClientWorkerObservationProvider,
+    CompositeWorkerObservationProvider, WorkspaceClientWorkerObservationProvider,
+};
+use worker::feature::contracts::{
+    WorkerObservationError, WorkerObservationProvider, WorkerObservationSubject,
+    WorkerObservationSubjectRef, WorkerSessionCapture,
 };
 #[cfg(feature = "ws-server")]
 use worker::ipc::protocol_session::{WorkerProtocolSessionStreams, live_log_entry_event};